A roof valley is the channel where two roof slopes meet. Because it collects water from both slopes, it carries more water than any other part of a tiled roof. Old galvanised valleys rust through, and debris piles up and pushes water under the tiles. Replacing a valley with Colorbond valley iron, a valley seal and properly fixed tiles is one of the most common tiled roof repairs in Melbourne.
The short answer
- Valleys carry water from two roof slopes
- Rust holes and overflowing debris are the usual failures
- New valleys use Colorbond valley iron
- Valley seals stop water and debris under the tiles
- Each cut valley tile must be fixed
Signs your valley needs work
- Water stains on the ceiling below a valley after heavy rain
- Rust, holes or flaking metal in the valley iron
- Leaves and debris built up along the valley
- Cut valley tiles that have slipped or cracked
- Old cement bedding along the valley edges breaking away
Light surface rust can sometimes be treated, but holes or heavy corrosion mean the valley iron needs replacing.
The parts of a tiled valley
| Part | Job | What we stock |
|---|---|---|
| Valley iron | The metal channel that carries water | Colorbond valley iron, 3 metre lengths |
| Valley seal | Stops wind-driven rain and debris getting under the cut tiles | Storm Seal, per 2 metre length or box of 54 |
| Valley clips | Fix the cut tiles along the valley | 85mm galvanised valley pegs |
| Cut valley tiles | Tiles cut to line up along the valley | Replacement tiles to match your roof |
The National Construction Code housing provisions require valley tiles, like ridge and hip tiles, to be fixed individually in wind classes N1 to N3.
How a valley is replaced
Walking on tiles cracks them and puts you at risk of a fall. WorkSafe Victoria treats falls from roofs as a serious hazard and puts edge protection ahead of ladders and harnesses. If you are not trained and equipped to work at height, use this guide to buy the right products and brief a roofer.
- Remove the cut tiles along both sides of the valley and stack them for reuse.
- Lift out the old valley iron and check the valley boards and battens underneath.
- Lay the new valley iron, lapping lengths in the direction of water flow.
- Fit the valley seal along each side.
- Relay the cut tiles, trimming with a diamond blade where needed, and fix each one with valley clips.
- Replace broken tiles with matching tiles and check the gutter where the valley discharges.
Common valley mistakes
- Patching holes with sealant: buys a few months at best. Rusted valley iron should be replaced.
- Laps the wrong way: each upper length must lap over the lower one so water cannot run back under the joint.
- Leaving out the valley seal: without it, wind-driven rain and leaves get under the cut tiles.
- Loose cut tiles: cut tiles that are not clipped can slip into the valley and block it.
- Mixing metals: keep fixings and adjoining metals compatible with the valley iron to avoid corrosion.
Old valleys were often bedded with cement mortar along the cut tiles. Modern valleys rely on valley seals and clips instead, which allow for roof movement and are easier to maintain.
Choosing a valley colour
Colorbond valley iron comes in pre-painted colours, so the valley can match the tiles, gutters or a restoration colour. If the roof is about to be restored, choose a valley colour that suits the new roof colour. We stock two valley iron options in 3 metre lengths; ask at the yard about current colours.
Keeping valleys clear
Most valley leaks start with debris. Leaves build up, slow the water, and during heavy rain it overflows under the tiles. Clear valleys and gutters regularly, especially under overhanging trees, and check after storms. Gutter protection mesh helps keep leaves out of the gutters where valleys discharge.
For regular valley and gutter clearing, our sister business PorterVac cleans gutters across Melbourne. For a full valley replacement, Royce Roofing repairs roof valleys.
Shopping list
- Colorbond valley iron and Storm Seal
- 85mm valley clips and clouts
- Replacement roof tiles for any broken cut tiles
- A diamond blade for cutting tiles and tin snips for the valley iron
- Flexible pointing if hips meeting the valley need repointing
Common questions
How do I know if my roof valley needs replacing?
Rust holes, flaking metal, ceiling stains below the valley and repeated overflowing are the common signs.
What is valley iron?
The metal channel, usually Colorbond, that carries water down the valley between two roof slopes.
What does a valley seal do?
It sits along the edges of the valley iron and stops wind-driven rain and debris getting under the cut tiles.
Do valley tiles need to be fixed?
Yes. The NCC requires valley tiles to be fixed individually in wind classes N1 to N3, usually with valley clips.
Can I reuse the old valley tiles?
Usually, if they are sound. Replace any that are cracked with matching tiles.
Related
Sources: NCC 2022 Housing Provisions Part 7.3: Roof tiles and shingles; WorkSafe Victoria: Prevention of falls in housing construction.
